1. Field of Invention
This invention relates generally to the field of retractable platforms, and more particularly to a chain or flexible member driven linear actuator for a retractable platform for a wide variety of components and uses for vertical as well as horizontal movement, depending on the application. Applications include utilization as a vertical retractable platform lift for components including computer monitors, T.V""s, kitchen appliances, guns, book shelves and pictures from within a cabinet or from under a floor or down from a ceiling, and utilization as a horizontal retractable platform device for similar components from within a wall.
2. Description of Prior Art Components such as T.V.""s and computers and their monitors etc. are seen as unsightly by many and take up valuable working space such as desk tops and tables when not in use. Other components such as guns are dangerous, and some components are valuable and would benefit from hidden storage. In addition, there are many spaces such as mobile homes and other small living spaces where it is desirable to maximize space. Hence, it is desirable to provide a means of storing components compactly out of sight within furniture, walls, ceilings and floors when not in use and when it is desired to use them, to provide a simple and efficient means of gaining access to them, with a cost effective product. Therefore, compactness, ease of use, economical manufacture, and performance, particularly the ability of the platform to remain parallel during operation and over time, dictated the design of the linear actuator platform.
In platform lifts suspended by multiple chains or other flexible members, hereafter referred to simply as chains generally, unequal distribution of load on the platform results in differential chain stretch over time, adversely affecting the ability of a platform to remain parallel. Therefore, it is an objective of the invention to accommodate chain stretch, and more importantly differential chain stretch in the design.
The above stated objectives are achieved with the present invention through a unique routing of chains through idler pulleys uniquely positioned and driven and the compactness of the design. For instance, both the routing / placement and the compactness result in a shorter length of chain thereby reducing the effects of stretch.
The prior art shows various ways of raising and lowering retractable platforms, yet not one is able to meet all the objectives of the present invention.
For example, U.S. Pat. No. 2,285,251 to Cochran for an Industrial Truck requires pulleys operating at different speeds.
U.S. Pat. No. 2,565,304 to Garstang et al for a Radio-Phonograph Cabinet does not provide for a compact design of the box, has additional horizontal forces combined with its vertical lifting forces, and is prone to failure due to its simple chain drive and reliance on a single pin stopping the chain.
U.S. Pat. No. 3,719,295 to Grace for a Controlled Mechanical Storage Device includes what is termed xe2x80x9cparalellogrammimg meansxe2x80x9d for horizontal movement of the carriage via driven flexible members, preferably chains, that are uniquely routed. This routing of the flexible members does not allow for the compactness of design, thereby necessitating a greater length of flexible member or chain, which creates issues of stretch resulting in lower performance and the need for adjustment.
U.S. Pat. No. 4,735,173 to Dubreuil for an Animal Transport Unit includes a moveable floor within a box from a lower to an upper position for ease in handling animals. This movement is accomplished with the utilization of rack and pinion means. U.S. Pat. No. 3,313,376 to Holland for a Lightweight Elevator similarly utilizes rack and pinion means. Rack and pinion means requires a significant manufacturing cost due to the need for precision components due to precision alignment constraints.
U.S. Pat. No. 5,469,936 to Lauga et al for a Support Device for an Item of Retractable Street Furniture is of a winch design and requires a continual feed of power to maintain the platform in the xe2x80x9cupxe2x80x9d position.
Accordingly, several objects of the present invention are to provide a linear actuator for a platform that:
a. Provides a lifting and retraction or pushing and retracting platform and mechanism for objects while utilizing a minimum number of parts;
b. Allows for a compact profile if necessary for space considerations;
c. Maintains the platform in a parallel plane;
d. Is simple and economical to manufacture and easy to maintain.
These and further objects will be apparent from the following description and drawings of the preferred embodiments thereof.